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71.
Recent results of experimental studies on magnetoelastic coupling in epitaxial monolayers are compiled and discussed in view of theoretical work. The observation of non‐bulk like magnetoelastic coupling in strained systems in experiment and theory is ascribed to an effective and strain‐dependent magnetoelastic coupling. It is described as a second‐order strain contribution to the energy density. We comment on the importance of inhomogeneous strain and of its relaxation for the magnetic anisotropy of nanostructures. 相似文献
72.
Feczk&#; Tivadar Muskot&#;l Ad&#;l G&#;l Lor&#;nd Sz&#;pv&#;lgyi J&#;nos Sebesty&#;n Anett Vonderviszt Ferenc 《Journal of nanoparticle research》2008,10(1):227-232
Superparamagnetic Ni–Zn ferrite nanoparticles were synthesized in radiofrequency thermal plasma reactor from aqueous solutions of Ni- and Zn-nitrates. The nanoparticles were studied for protein purification performance in both quantitative and qualitative terms. For comparison, experiments were also performed by Ni-charged affinity chromatography. It was proved that the Ni–Zn ferrite nanoparticles effectively purified histidine-tagged proteins with a maximum protein binding capacity of about 7% (w/w). Gel electrophoresis demonstrated better purification characteristics for magnetic nanoparticles than for affinity chromatography.
相似文献73.
R. Kirschner 《Zeitschrift fur Physik C Particles and Fields》1995,65(3):505-510
We study the pairwise interaction of reggeized gluons and quarks in the Regge limit of perturbative QCD. The interactions are represented as integral kernels in the transverse momentum space and as operators in the impact parameter space. We observe conformal symmetry and holomorphic factorization in all cases. 相似文献
74.
The article reviews recent measurements using the Magnetization induced Second Harmonic Generation (MSHG) from ultrathin metallic films and multilayers. Emphasis is put on the high surface and interface sensitivity and the influence of ‘quantum well states’ (QWS). With the example of a Ni/Cu/Ni/Cu(001) multilayer structure we show that there is a net (magnetic) contribution from the symmetrically buried lower Ni layer because of the presence of QWS in the Cu spacer layer, which makes the observation of antiferromagnetic coupling in the Ni/Cu/Ni/Cu(001) structure possible with MSHG. 相似文献
75.
The quantitative interpretation of high resolution electron micrographs requires image processing. We present a new neural network (NN) based method of determining the local composition and thickness in micrographs of III–V semiconductors. The NNs are trained with simulated HREM patterns of AlGaAs including an appropriate amorphous layer modelling. By comparing simulated and experimental images, we can estimate the amorphization depth of the samples. Neural networks suppress the correlated noise from amorphous surface layers and distinguish between variations of the sample thickness and the semiconductor composition. 相似文献
76.
R. Zimny H. Hagedorn H. Winter J. Kirschner 《Applied Physics A: Materials Science & Processing》1988,47(1):77-81
We observe the emission of circularly polarized light after grazing scattering of fast ions at a magnetized Fe(110) surface. Changing the state of magnetization of the target affects the polarization of the emitted light due to capture of spin polarized electrons. Some aspects of atom-surface interaction and investigations of surface magnetism are discussed. 相似文献
77.
78.
Jennifer Solarczek Dr. Felix Kaspar Pia Bauer Prof. Anett Schallmey 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(72):e202202343
Halohydrin dehalogenases are promiscuous biocatalysts, which enable asymmetric ring opening reactions of epoxides with various anionic nucleophiles. However, despite the increasing interest in such asymmetric transformations, the substrate scope of G-type halohydrin dehalogenases toward cyclic epoxides has remained largely unexplored, even though this subfamily is the only one known to display activity with these sterically demanding substrates. Herein, we report on the exploration of the substrate scope of the two G-type halohydrin dehalogenases HheG and HheG2 and a newly identified, more thermostable member of the family, HheG3, with a variety of sterically demanding cyclic epoxides and anionic nucleophiles. This work shows that, in addition to azide and cyanide, these enzymes facilitate ring-opening reactions with cyanate, thiocyanate, formate, and nitrite, significantly expanding the known repertoire of accessible transformations. 相似文献
79.
Marcel Staar Steffi Henke Prof. Wulf Blankenfeldt Prof. Anett Schallmey 《ChemCatChem》2022,14(9):e202200145
A major drawback for practical application of halohydrin dehalogenase HheG in biocatalysis is its rather low thermal stability and low organic solvent tolerance. We therefore pursued a stabilization of HheG via immobilization as cross-linked enzyme crystals. Since glutaraldehyde inactivates HheG, we introduced a cysteine residue in the crystal interface, which enabled thiol-specific cross-linking at well-defined cross-linking sites. Variant HheG D114C displayed improved crystallizability and yielded stable and catalytically active CLECs using bis-maleimidoethane as cross-linker. Effective cross-linking at the predefined site could be confirmed via the CLEC crystal structure. Compared to soluble enzyme, the CLECs displayed significantly improved stability and activity at higher temperatures, lower pH values and in the presence of water-miscible organic solvents, which enabled their reuse over 21 days in the azidolysis of cyclohexene oxide. 相似文献
80.
Sven Kirschner Matthew Peters Kang Yuan Marina Uzelac Michael J. Ingleson 《Chemical science》2022,13(9):2661
Despite the general high fluorophilicity of boron, organoboranes such as BEt3 and 3,5-(CF3)2C6H3–BPin are shown herein for the first time, to our knowledge, to be effective (solid to solution) phase-transfer catalysts for the fluorination of certain organohalides with CsF. Significant (up to 30% e.e.) chiral induction during nucleophilic fluorination to form β-fluoroamines using oxazaborolidine (pre)catalysts and CsF also can be achieved. Screening different boranes revealed a correlation between calculated fluoride affinity of the borane and nucleophilic fluorination reactivity, with sufficient fluoride affinity required for boranes to react with CsF and form Cs[fluoroborate] salts, but too high a fluoride affinity leading to fluoroborates that are poor at transferring fluoride to an electrophile. Fluoride affinity is only one component controlling reactivity in this context; effective fluorination also is dependent on the ligation of Cs+ which effects both the phase transfer of CsF and the magnitude of the [Cs⋯F-BR3] interaction and thus the B–F bond strength. Effective ligation of Cs+ (e.g. by [2.2.2]-cryptand) facilitates phase transfer of CsF by the borane but also weakens the Cs⋯F–B interaction which in turn strengthens the B–F bond – thus disfavouring fluoride transfer to an electrophile. Combined, these findings indicate that optimal borane mediated fluorination occurs using robust (to the fluorination conditions) boranes with fluoride affinity of ca. 105 kJ mol−1 (relative to Me3Si+) under conditions where a signficant Cs⋯F–B interaction persists.Simple boranes with the optimal fluoride ion affinity are effective as catalysts for phase transfer nucleophilic fluorination with CsF. 相似文献